stm32f1x_cl: Add initial support for STM32F1x connectivity line

This currently supports the stm32f107, but support will be added for
the F105 shortly (missing a linker script and I can't properly test
without a devkit).

cpu/arm/stm32f1x_cl/clock.c

@@ -0,0 +1,78 @@
+#include <sys/clock.h>
+#include <sys/cc.h>
+#include <sys/etimer.h>
+#include <debug-uart.h>
+
+#include <libopencm3/cm3/systick.h>
+
+static volatile clock_time_t current_clock = 0;
+static volatile unsigned long current_seconds = 0;
+static unsigned int second_countdown = CLOCK_SECOND;
+
+void sys_tick_handler(void) __attribute__ ((interrupt));
+
+void
+sys_tick_handler(void)
+{
+  current_clock++;
+  if(etimer_pending() && etimer_next_expiration_time() <= current_clock) {
+    etimer_request_poll();
+    /* printf("%d,%d\n", clock_time(),etimer_next_expiration_time       ()); */
+  }
+
+  if(--second_countdown == 0) {
+    current_seconds++;
+    second_countdown = CLOCK_SECOND;
+  }
+}
+
+
+void
+clock_init()
+{
+  systick_set_clocksource(STK_CTRL_CLKSOURCE_AHB_DIV8);
+
+  /*72mhz / 8 / 1000 */
+  systick_set_reload(MCK / 8 / CLOCK_SECOND);
+
+  systick_interrupt_enable();
+  systick_counter_enable();
+}
+
+clock_time_t
+clock_time(void)
+{
+  return current_clock;
+}
+
+unsigned long
+clock_seconds(void)
+{
+  return current_seconds;
+}
+
+/* TODO: This code needs to be evaluated for the stm32f107 and
+ * implemented
+ */
+#if 0
+/* The inner loop takes 4 cycles. The outer 5+SPIN_COUNT*4. */
+
+#define SPIN_TIME 2             /* us */
+#define SPIN_COUNT (((MCK*SPIN_TIME/1000000)-5)/4)
+
+#ifndef __MAKING_DEPS__
+
+void
+clock_delay(unsigned int t)
+{
+#ifdef __THUMBEL__
+  asm
+    volatile
+    ("1: mov r1,%2\n2:\tsub r1,#1\n\tbne 2b\n\tsub %0,#1\n\tbne 1b\n":"=l"
+     (t):"0"(t), "l"(SPIN_COUNT));
+#else
+#error Must be compiled in thumb mode
+#endif
+}
+#endif
+#endif /* __MAKING_DEPS__ */